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BIBLIOGRAPHY
Anal Sphincter

The Anal Sphincter
 
The anal sphincter is found at the end of the anal canal. It is where the food ends up after it has passed through the small and large intestines, and important nutrients have been removed. The anal sphincter is made up of 2 main muscles. These are the internal anal sphincter and the external anal sphincter.
 
For diagrams of the anal sphincter, see our section "Diagrams".

 
Internal Anal Sphincter
    
   The internal anal sphincter is a thin, white muscle wrapped around the anal canal. This muscle will contract to move feces, and is involuntary. This muscle will also help prevent small amounts of liquid or gas from escaping the anal sphincter. The muscle is smooth and resembles that of the intestinal muscles.

 
External Anal Sphincter
 

The external anal sphincter is thicker and red in colour. It is the voluntary muscle that allows you to control when you excrete feces. This muscle is wrapped around the internal anal sphincter, and is what you clench when you feel you have to go to the bathroom. It can stretch to allow feces to leave the body. This is the last part of the excretory tract and is where the feces will exit the body.

Finally, the feces is released through the anus. The anal fissure is the hole in which the feces is passed through. Fecal matter should be solid and medium to dark brown in colour. Green runny feces may indicate diarrhea, while black feces may indicate internal bleeding.

How The Wastes Come Out